1. Field of the Invention
This invention relates broadly to oil and gas exploration or production. More particularly, this invention relates to systems and methods for testing and analyzing the compatibility of a reservoir with treating fluids, wellbore fluids, and the compatibility of these fluids with each other.
2. State of the Art
It is well known in the arts of oil and gas exploration and production that it can be advantageous to introduce certain fluids into the well bore and/or the formation. For example, during drilling, fluid is typically introduced into the annulus between the drill string and the wellbore. During exploration, fluid may be injected into the formation in order to obtain information related to the formation. During production, certain additives may be injected into the formation to enhance production.
Before introducing any significant quantity of fluid into the wellbore or the formation, it is desirable to determine whether the fluid will create an undesirable reaction. Thus, one or more fluid compatibility tests are preferably performed prior thereto. The testing process may include checks for compatibility of treating fluids and/or wellbore fluids with a reservoir formation and reservoir fluids. In general, fluids are compatible if their mixture does not adversely affect the permeability of the formation, or cause the development of any undesirable products (such as asphaltenes, waxes, or scale) in the wellbore, production tubing, surface facilities, and flowlines.
Where treating fluids are to be utilized, the treating fluid should remove existing damage (typically caused during drilling) without creating additional damage such as precipitates or emulsions through interactions with the formation rock or fluids. In extreme cases, it is possible that a seemingly benign fluid can create significant reactions that may permanently damage the permeability of the reservoir.
Presently, fluid compatibility tests are performed in a laboratory using fluids obtained from a wellbore and/or formation. In some cases, the fluids are obtained using a borehole tool which samples formation fluids as is well known in the art. A tool is lowered into a borehole which traverses a formation and is then brought into contact with the formation. A formation fluid sample is obtained by reducing the pressure in the borehole tool below the formation pressure. The tool with the fluid sample is then brought to the surface. The fluid sample is retrieved and sent to a laboratory for testing. Other methods for obtaining a fluid sample are known in the art, and include retrieving a sample from a producing well, during well testing or during well production exploitation.
The previously incorporated applications disclose downhole tools for formation testing via injection of non-formation (test) fluids into the formation and thereafter sampling the formation fluids. The tools include various sensors and circuits for monitoring and analyzing downhole formation fluid characteristics. However, it is desirable that, before injecting anything into the formation, compatibility tests be performed. It would be desirable if fluid compatibility tests could be performed downhole either contemporaneous with or prior to the testing which requires injection of non-formation fluids into the formation.